Electromagnet



UNITED STATES PATENT" OFFICE.

BENJAMIN MCINNERNEY, COUNCIL BLUFFS, IOWA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTROMAGNET.

, Specification of Letters Patent. t t Jan. 11, 1921.

Application filed March 28, 1917. Serial No. 157,923.

To all whom it may concern.

Be it known that I, BENJAMIN MGINNER- NEY, a citizen of the UnitedStates, and a resident of Council Bluffs, in the county of Pottawattamieand State of Iowa, have invented a new and useful Improvement inElectromagnets, of which the following is a specification.

My invention relates to electromagnets,

member from the armature member is of maximum width. The pull increasesrapidly as the armature member moves toward the core member and thewidth of the air gap is diminished. The result is to cause the armaturemember to engage the stationary part with which it coacts withaconsiderable shock or impact, since the force exerted upon it is amaximum at the instant of engagement.

The noises incident to the engagement of the rapidly moving parts 'areparticularly noticeable in connection with relatively largeelectromagnets where 'the' moving parts have considerable weight. Whenelectromagnets are employed in connection with elevators and hoists andare mounted at the tops of the shafts or in overhead structures, thenoises are particularly objectionable.

It is possible to partially avoid the undesirable features mentionedabove by the employment of dashpots or by submerging the electromagnetsin oil. These arrangements are, however, unsatisfactory for the reasonthat it .is necessary to make occasional adjustments of dashpots inorder that they may be effective. It is necessary, also, that tanks forsurrounding oil-submerged electromagnets be maintained in such conditionas to prevent leakage of the oil and that the supply of oil bereplenished at intervals. It has been found, in practice,that theattendantsof elevators and similar machines neglect their duties inthese regards" and the devices become practically useless.

The arrangement, which comprises the subject matter of the presentapplication re- Y electromagnet.

operation of the retarding device is desir-' quires no adjustment orattention after it is installed. A segment of conducting material, such,for example, as iron, steel or copper, is operatively connected to themovable armature member of an electromagnet and s arranged to movethrough a path that is lmmedlately adjacent to the armature member andcore member during the closing movement of the armature member. Thedamplng segment, as it may be termed, passes through a portion of themagnetic field of the 'electromagnet and the eddy currents, whlch areset up in the segment, cause a retardlng effect that is proportional tothe strength of the field of the electromagnet and to the speed at whichthe segment is actuated.

The retarding force exerted by the dampmg segment increases as thearmature member approaches its closed position since an increasedportion of the segment is adjacent to the air gap between the members ofthe This characteristic of the able since the retarding force is ofmaxi- -mum. degree when the force actuating the core member to itsclosed position is also at a maximum.

While my invention is adapted to be employed in connection withelectromagnets of the general character illustrated in the drawing, itis preferably employed in connection with electromagnets such as thatshown and described in my Patent No. 1,238,313, granted August 28, 1917,and assigned to the Westinghouse Electric & Manu acturing Co.

In the accompanying drawing, Figure 1 is an end view, in elevation, ofan electromagnet constructed in accordance with my invention. Fig. 2 isa side view, in elevation, of a portion of the electromagnet shown inFig. 1.

An electromagnet comprises a stationary I magnetizable member 1 whichmay have any deslred number of polar projections. .The core member 1 maybe provided with any suitable number of coils in accordance with thecharacter of the source of energy, a

any suitable mechanisms, such, for example as brakesfor elevators.

A member 7, which may be termed a damping segment, is pivotally mountedat 8 for movement through a path immediately adjacent to thecorresponding ends of the core member 1 and the armature member 3. Themember 7, which is of conducting material, is operatively connected tothe armature member 3 by means of a link 9. If such arrangement isnecessary or desirable, a similar member 7 may be mounted at the otherend of the electromagnet.

The damping segment 7 is preferably maintained in engagement with thecore member 1 in any desired manner, as by means of a spring 10. Thispreferred arrangement serves a double purpose; first, the dampingsegment'is thereby prevented from rattling-after it wears loose andsecondly, if the segment is made of steel, it has been found that agreater damping effect is thereby obtained, probably due to frictionbetween the segment and the core member 1.

It may be assumed that the armature member 3 occupies its open positionand the damping segment 7 occupies its corresponding position which isindicated by dot-anddash lines, 'Fig. 1. It will be noted that, when thedamping segment 7 occupies its normal position, substantially no part ofthe air gap between the armature member 3 and the core member 1 isbridged by it.

It may be assumed, further, that the circuit of the coil 2 has beencompleted and the latter energizes the magnetic circuits of the coremember 1. The armature member 3 is drawn downwardly with a constantlyincreasing pull as the reluctance of the magnetic circuit is diminishedby the decrease in the width of the air gap.

Simultaneously with the movement of the armature member 3, the dampingsegment 7 is actuated in a clockwise direction about its point ofpivotal support to bridge an increasing portion of the air gap betweenthe end of the armature member 3 and the corresponding portion of thecore member 1. The damping segment 7 traverses part of the ma eticcircuit of the electromagnet and ed y currents are induced which causethe segment to operate as a damper to retard t e closing movement of thearmature.

The retarding force increases by reason of the fact that a largerportion of its surface bridges the air gap, and, in addition, the speedof the armature member 3 tends to increase as it approaches the coremember 1. The result is to effectively retard the movement of thearmature member 3 and thereby prevent the noise that is ordinarilyincident to the striking of the pole faces of the core member.

It will be noted that an arrangement constructed in accordance with myinvention is much more simple and economical than the methods of theprior art previously discussed. After the damping device is installed,neither attention nor adjustment is necessary. The device operatesautomatically and with a force that varies in accordance with theoperating conditions of the electromagnet in connection with which it isemployed. My. invention is particularly adapted for use in connectionwith electromagnets embodied in controlling mechanisms such, forexample, as elevators in hospitals, hotels and apartment houses whereunusual noises are particularly undesirable.

I claim as my invention:

1. In anelectromagnet, the combination with a core member and anarmature member coacting therewith of means cooperating with themagnetic Held of said electromagnet. for retarding the movement of saidarmature member with an increasing effect as the armature is actuated toits closed position.

2. In an electromagnet, the combination with a core member and anarmature member coacting therewith, of means for retarding the movementof said armature member with a varying eflect, said means comprising amovable member of conducting material for shunting a portion of themagnetic flux of said electromagnet.

3. In an electromagnet, the combination with a core member and anarmature member coacting therewith, of means comprising a movablememberof conducting material operativel connected to said armaturemember and cooperating with the magnetic field of said electromagnet,for retarding the movement of the latter member to its closed position.

4:. In an electromagnet, the combination with a stationary portion and amovable portion coacting therewith and normally separated therefrom by agap, of means for retarding the closing movement of said movableportion, said means comprising a movable conducting member adjacent tosaid gap and cooperating with the magnetic flux of said electromagnet.

5'. In an electromagnet, the combination with a stationary portion and amovable portion coacting therewith, of means for retarding the closingmovement of said movable portion, said means comprising a movable memberof conducting material adjacent to each of said portions and cooperatingwith the magnetic flux of said electromagnet and operatively connectedto the movable portion.

6. In an electromagnet, the combination with a stationary portion and amovable portion coacting therewith, of means for retarding the closingmovement of said movable conducting portion, said means comprising amovable member adjacent to each of said portions and cooperating withthe magnetic flux of said electromagnet and arranged to present anincreasing surface to the gap between them as the movable portionapproaches its closed position.

7. The combination with an electromagnet having a pair of relativelymovable members normally separated by a gap, of means cooperating withthe magnetic flux of said electromagnet for creating eddy currents inthe neighborhood of said gap for retarding the relative movement of saidmembers.

8. The combination with an electromagnet having a stationary core memberand a movable armature member, of a conducting member and means formoving said conducting member in the magnetic field of saidelectromagnet during the closing movement of said armature member tocreate eddy currents for retarding said movement.

9. The combination with an electromagnet comprising a stationary coremember and an armature member pivotally mounted thereon, of a conductingsegment pivotally mounted upon said stationary member for movementthrough the magnetic field of said electromagnet, and a link connectingsaid armature member to said conducting segment whereby movement of saidarmature member is controlled by said segment.

10. The combination with an electromagnet having a stationary coremember and a movable armature member normally separated therefrom by agap, of a conducting member normally distant from said gap and movableinto the neighborhood of said gap and means for so moving saidconducting member as to increase the portion of said conducting memberin the neighborhood of said gap in accordance with a decrease in thesize of said gap.

In testimony whereof, I have hereunto subszcribed my name this 19th dayof March, 191

BENJAMIN MQINNERNEY.

